Blasthole drills are large earth drilling machines typically used in mining operations to drill holes for explosives. A conventional blast hole drill comprises a frame supported by crawlers for movement over the ground. A drill deck having a large rectangular opening is supported by the frame. A mast is supported by the frame for movement relative to the frame between a vertical position and a plurality of non-vertical positions. A drill pipe or drill string is supported relative to the mast, and a drill cutter bit is connected to a lower end of the drill pipe. The drill pipe extends through the opening of the drill deck and the shape of the opening allows the drill pipe to be positioned at the desired angle relative to the drill deck for drilling purposes. A rotary head engages an upper end of the drill pipe and moves along the mast. The rotary head rotates the drill pipe, and thus the drill cutter bit, into the ground.
During operation, when a drill cutter bit is caused to rotate and move downward into the ground, the drilled earthen material, such as dust, rock chips, rubble, and the like, travels up alongside the drill pipe and out of the drilled hole such that the drilled material is thereafter collected in a curtained-off area between the blasthole drill and the ground. In an effort to prevent escape of the earth cutting dust and the like into the surrounding environment, it is known to seal the opening of the drill deck and, in particular, to seal the opening around the drill pipe relative to the drill deck.
Known mechanisms designed to seal a substantial portion of the opening of a drill deck include a plurality of overlapping, typically square or rectangular, rigid metal plates which are adjustably secured to a track on the drill deck. The metal plates are positioned one above another so as to define overlapped portions between adjacent metal plates whereby the overlapped portions are generally perpendicular to the plane in which the drill pipe moves. As is generally known, the location of the metal plates with respect to each other depends on the angle of the drill pipe relative to the drill deck as the drill pipe extends through the opening of the drill deck. For example, if the drill pipe is in a vertical position, all of the metal plates are typically located to one side of the drill pipe. On the other hand, if the drill pipe is in a non-vertical position, one or more of the metal plates are typically located on one side of the drill pipe and one or more of the metal plates are typically located on an opposite side of the drill pipe. Although these metal plates are known to substantially seal the majority of the opening of the drill deck, the metal plates are not typically designed to independently seal the opening directly around the drill pipe. Thus, it is generally known to provide a dust cone and a dust cone carrier to be used in cooperation with the metal plates so as to seal the opening around the drill pipe. The dust cone carrier is typically also a metal plate which is adjustably secured to a track of the drill deck in much the same fashion as the metal plates. The dust cone carrier generally includes an elliptical hole through which the drill pipe can extend. The elliptical hole allows the drill pipe to pass through the dust cone carrier in any operable angular position relative to the drill deck. A dust cone of known material is secured to the dust cone carrier and extends below the dust cone carrier into the curtained-off area between the blasthole drill and the ground. The dust cone is generally configured such that the larger diameter hole of the dust cone is positioned near or adjacent the bottom side of the dust cone carrier, and the smaller diameter hole of the dust cone is positioned near, or in actual contact with, the drill pipe. In some known mechanisms, one or more plastic or rubber-like sheets having circular holes therethrough may be located internal to the dust cone in order to surround and possibly come into contact with the drill pipe.
In such known mechanisms, as the drilled material travels up alongside the drill pipe and out of the drilled hole, the shape and location of the dust cone is designed to prevent the drilled material from continuing on up alongside the drill pipe and also cause the drilled material to fall into the curtained-off area between the blasthole drill and the ground. The plastic or rubber-like sheets, if utilized, are intended to prevent any drilled material which happens to pass between the small diameter hole of the dust cone and the outer surface of the drill pipe from continuing farther up alongside the drill pipe. As a result, in conjunction with the metal plates, dust and the like is prevented from escaping into the atmosphere through the opening in the drill deck of a blasthole drill.
There are other known mechanisms for sealing an opening around a structure, but such mechanisms are generally not suitable for use in typical blasthole drill equipment for reasons commonly known to those skilled in the art.